very weird – i can’t reproduce that. When editing, the correct content shows up? Can you send me your site so I can register and see it in action?

Technically, when passed in the activity_id – the bp_activity_add function will switch to update instead of an insert. the activity_id is taken from $bp->action_variables[0] and then also validated against a nonce on the edit screen. (any chance you have a different url structure?)

After deactivating all plugins except BP, the double entries were still there, so I had a look at files I’ve edited and voilà: the problem was in my functions.php. There was an additional call to activity/entry.php… doh! Realized that the function in question was kind of redundant so, after deleting it, problem solved.